Every now and then someone submits a memoir to the Wordos. This is usually confusing to the table because A) memoir is typically an idea plot hidden underneath a event plot, and B) it can be difficult to look at just the text of a memoir and critique protagonist in the memoir as a well-written character and not the author as a person.
One of the things that I learned from a memoir writing class was that a good memoir has a rhythm or procession of symbols that can be discovered within individual vignettes, and this rhythm is mirrored in the overall memoir. In general, the vignette follows the form stasis, discovery, tension, more tension, crisis, conclusion. This was extremely helpful to realize when I went to see the movie, "Before Night Falls," based on a posthumous memoir of Reinaldo Arenas. The movie was much less confusing once I realized that every little story (and the entire piece) was using the metaphor of a rising above everything in a balloon which is out of control and subsequently crashes.
It was suggested by our instructor that the events, settings and people we write repeat -- sort of like the same way the same symbols would aggregate in a dream journal. She further suggested that we write stories about ourselves to explore a question we are asking ourselves. For example, in my class assignment, it was pointed out to me that I chose to retell events involving attempts at expansion by ignoring rules of physical safety (a canoe stunt, trancing out on the dance floor, a near-accident skydiving, and an automobile-bicycle collision). My memoir was organized around self-identity and boundaries.
If you choose to cast a life event as a memoir, you might want to ask, "What does this event (or series of events) mean to me?" Or you might look for emotional similarities. Or you might ask, "What have I learned at the end of this that I didn't at the beginning?" Also, truth is stranger than fiction. It may be true that X happened in real life, but it still needs to be plausible in a manuscript -- so for the sake of readability, an author can and will take poetic liberties with events.
In terms of critiquing memoir -- or any manuscript for that matter -- it's also helpful to keep in mind the narrator of a manuscript is a character created by the author, and that an author is not one of their characters. In memoir, it can be easy to lose track of the boundaries between the author as a person, the author's persona, and characters in the manuscript. Address the text, not the author.
The American form for memoir was set by Frank Conroy in "Stop-Time." (It's not always cheery reading.) An interesting look at author, persona and memoir may be found in Ruth Reichi's "Garlic and Sapphires."